Various systems utilizing a plurality of data-entry terminals have been heretofore developed which enable the entry of data for data processing from a plurality of different locations. For example, prior systems have utilized a plurality of point-of-sale terminals in a retail store environment to enable sales data to be entered at a plurality of locations about a retail establishment. In such prior point-of-sale systems, the terminals have often been connected to a common data bus and the data directed to a common computer host which may be located at the retail establishment or at a remote location. Such systems are relatively bulky and expensive due to the requirement of a large and complex separate host data processing computer or controller for storing input data.
In order to eliminate the requirement of a separate on-line host data processing computer, stand-alone terminals have been previously developed utilizing magnetic storage cassettes which are used to record sales data from each terminal. The cassettes may then be subsequently removed and taken to a remote location for subsequent processing.
In point-of-sale terminal system, it is necessary to perform arithmetic operations on sales data with the use of various function programs. In one type of point-of-sale system using a magnetic tape cassette, function programs for operating on point-of-sale data are permanently stored in non-volatile memories in each of the terminals. In another type of such prior system, function programs are input into each of the terminals at the beginning of the day when the system is powered up. In both types of prior systems, there has been a requirement for storage in each of the terminals for function programs which are required to be executed during operation of the terminals. Such prior systems have thus required a plurality of separate storage facilities in each point-of-sale terminal to provide the desired operation.
Moreover, such prior multiple terminal point-of-sale systems have not been completely satisfactory with respect to ease of adaptability to various desired configurations and have not been easily changeable in configuration to accommodate breakdown of one or more portions of the system. For example, in such prior systems, in order to change the interconnection of a master terminal in the system, extensive cable rearrangements or line switching changes have generally been required.
A need has thus arisen for a point-of-sale data-entry terminal system wherein the data-entry terminals are self-contained in unitary portable housings without the requirement of additional data recording housing and the like. A need has also arisen for a point-of-sale data terminal wherein permanent storage for function programs is not required for each terminal, and wherein the configuration of the system may be easily reconfigured without the requirement of cable rearrangement or line switching. A need also exists for a point-of-sale data-entry terminal system wherein primary bus control and central storage may be easily changed from one terminal to another to provide backup in case of a malfunction. Such changeover should be by simple operator action at the terminal keyboard instead of extensive cable rearrangement or line switching.